The embodiments described herein relate generally to medical devices for therapeutic electrical energy delivery, and more particularly to systems and methods for delivering electrical energy in the context of ablating tissue rapidly and selectively by the application of suitably timed pulsed voltages that generate irreversible electroporation of cell membranes, in conjunction with the application of suitable regional cooling to enhance electroporation selectivity and efficacy.
In the past decade or two the technique of electroporation has advanced from the laboratory to clinical applications, while the effects of brief pulses of high voltages and large electric fields on tissue has been investigated for the past forty years or more. It has been known that the application of brief high DC voltages to tissue, thereby generating locally high electric fields typically in the range of hundreds of Volts/centimeter can disrupt cell membranes by generating pores in the cell membrane. While the precise mechanism of this electrically-driven pore generation or electroporation is not well understood, it is thought that the application of relatively large electric fields generates instabilities in the lipid bilayers in cell membranes, causing the occurrence of a distribution of local gaps or pores in the membrane. If the applied electric field at the membrane is larger than a threshold value, the electroporation is irreversible and the pores remain open, permitting exchange of material across the membrane and leading to apoptosis or cell death. Subsequently the tissue heals in a natural process.
Some known processes of adipose tissue reduction by freezing, also known as cryogenically induced lipolysis, can involve a significant length of therapy time. In contrast, the action of irreversible electroporation can be much more rapid. Some known tissue ablation methods employing irreversible electroporation, however, involve destroying a significant mass of tissue, and one concern the temperature increase in the tissue resulting from this ablation process.
While pulsed DC voltages are known to drive irreversible electroporation under the right circumstances, the examples of electroporation applications in medicine and delivery methods described in the prior art do not sufficiently discuss specificity and rapidity of action, or methods to treat a local region of tissue with irreversible electroporation while not applying electroporation to adjoining regions of tissue.
Thus, there is a need for selective energy delivery for electroporation and its modulation in various tissue types as well as pulses that permit rapid action and completion of therapy delivery. There is also a need for more effective generation of voltage pulses and control methods, as well as appropriate devices or tools addressing a variety of specific clinical applications. Such more selective and effective electroporation delivery methods can broaden the areas of clinical application of irreversible electroporation including therapeutic treatment to reduce the volume of adipose or fat tissue and the treatment of tumors of various types.